1. Field of the Invention
The present invention relates to a solid-state imaging device in which airtight sealing is provided between a transparent substrate and a solid-state imaging element, a method for producing the same device, and a mask which can be used for producing the same device.
2. Description of the Related Art
In recent years, the number of solid-state imaging devices mounted on a portable information apparatus is increasing. A solid-state imaging device mounted on a portable information apparatus includes a solid-state imaging element having a light receiving portion. The solid-state imaging element converts light from an object, which is incident on the light receiving portion, into an image signal. A peripheral integrated circuit for processing the image signal converted by the solid-state imaging element is mounted on the solid-state imaging element. The thus-configured solid-state imaging device is required to be sufficiently light-weighted, thin, and compact to be mounted on a portable information apparatus.
Japanese Laid-Open Patent Publication No. 6-204442 discloses a solid-state imaging device configured to provide airtight sealing between a transparent substrate and a solid-state imaging element which is included in the solid-state imaging device such that a light receiving portion of the solid-state imaging element is opposed to the transparent substrate. FIG. 16 is a cross-sectional view of a conventional solid-state imaging device 90. The solid-state imaging device 90 includes a transparent substrate 92 which transmits light therethrough. A rectangular parallelepiped-like solid-state imaging element 93 is mounted on the transparent substrate 92. On the side of a surface of the solid-state imaging element 93 which is opposed to the transparent substrate 92, alight receiving portion 94 including a plurality of photodiodes is provided in the solid-state imaging element 93. A protruding electrode 95, which electrically connects conductor wires formed on the transparent substrate 92 to the solid-state imaging element 93, is located on the same surface of the solid-state imaging element 93. The light receiving portion 94 of the solid-state imaging element 93 is provided so as to be opposed to the transparent substrate 92, i.e., the solid-state imaging element 93 is mounted face-down on the transparent substrate 92. A sealing resin 96 for providing airtight sealing between the solid-state imaging element 93 and the transparent substrate 92 is formed around the periphery of the solid-state imaging element 93.
The thus-configured solid-state imaging device 90 is produced in the following manner. Firstly, the protruding electrode 95 on the solid-state imaging element 93 is connected to the conductor wires formed on the transparent substrate 92, such that the light receiving portion 94 is opposed to the transparent substrate 92. The solid-state imaging element 93 is bonded face-down to the transparent substrate 92. The sealing resin 96 for providing airtight sealing between the solid-state imaging element 93 and the transparent substrate 92 is dispensed along the periphery of the solid-state imaging element 93. Next, the sealing resin 96 dispensed along the periphery of the solid-state imaging element 93 is cured so as to provide airtight sealing between the solid-state imaging element 93 and the transparent substrate 92. Note that a printing technique may be employed for applying the sealing resin 96 to the solid-state imaging element 93, which is mounted face-down on the transparent substrate 92 and is covered by a mask, along the periphery of the solid-state imaging element 93.
In the thus-configured solid-state imaging device 90, light incident on the transparent substrate 92 from a surface opposite to that opposed to the solid-state imaging element 93 is transmitted through the transparent substrate 92 and then enters the light receiving portion 94 provided in the solid-state imaging element 93. The solid-state imaging element 93 converts the incident light, which has entered the light receiving portion 94, into an image signal and outputs the image signal from an output terminal (not shown).
International publication WO 97/02596 pamphlet discloses a solid-state imaging device 80 configured to provide airtight sealing between a transparent substrate and a solid-state imaging element which is included in the solid-state imaging device such that a light receiving portion of the solid-state imaging element is opposed to the transparent substrate. FIG. 17 is a cross-sectional view of the solid-state imaging device 80. In FIG. 17, elements similar to those described in conjunction with the solid-state imaging device 90 and with reference to FIG. 16 are denoted by the same reference numerals, and detailed description thereof will be omitted. The solid-state imaging device 80 of FIG. 17 differs from the solid-state imaging device 90 of FIG. 16 in that a sealing resin 86 for providing airtight sealing between the solid-state imaging element 93 and the transparent substrate 92 is formed so as to continuously cover both of the periphery of the solid-state imaging element 93 and a surface of the solid-state imaging element 93 opposite to that opposed to the transparent substrate 92.
The thus-configured solid-state imaging device 80 is produced in the following manner. Firstly, as in the case of the solid-state imaging device 90 of FIG. 16, the protruding electrode 95 on the solid-state imaging element 93 is connected to conductor wires formed on the transparent substrate 92, such that the light receiving portion 94 is opposed to the transparent substrate 92. The solid-state imaging element 93 is bonded face-down to the transparent substrate 92. The sealing resin 86 for providing airtight sealing between the solid-state imaging element 93 and the transparent substrate 92 is dispensed so as to completely cover the solid-state imaging element 93. Next, the sealing resin 86 continuously applied to the solid-state imaging element 93 along the periphery thereof and on a surface thereof which is not opposed to the transparent substrate 92 is cured so as to provide airtight sealing between the solid-state imaging element 93 and the transparent substrate 92.
Japanese Laid-Open Patent Publication No. 10-256470 discloses still another conventional solid-state imaging device configured such that a second semiconductor chip adheres to a first semiconductor chip adhering to an island-shaped layer. FIG. 18 is a cross-sectional view of a solid-state imaging device 70 disclosed in the above-mentioned publication. The solid-state imaging device 70 includes an island-shaped layer 71. A first semiconductor chip 72 adheres to the island-shaped layer 71 via a first adhesive 74. A second semiconductor chip 73 adheres to the first semiconductor chip 72 via a second adhesive 75. The second adhesive 75 contains spherical silicon particles (a filler) 99 each having a particle size of 20 microns to 40 microns.
However, in the configurations of the solid-state imaging devices 80 and 90 shown in FIGS. 17 and 16, respectively, in order to mount a peripheral integrated circuit for processing an image signal converted by the solid-state imaging element 93 on the solid-state imaging element 93, as described above, the number of steps required is increased. Specifically, it is necessary to perform the steps of: applying a die bond paste for die bonding a peripheral integrated circuit to the solid-state imaging element 93 after the sealing resin 96 for providing airtight sealing between the solid-state imaging element 93 and the transparent substrate 92 is cured; and curing the die bond paste after the peripheral integrated circuit is die bonded to the solid-state imaging element 93.
Further, in order to prevent the die bond paste from contaminating the top surface of the peripheral integrated circuit and from adhering to a die bond tool, the amount of the die bond paste is required to be controlled according to the outer shape of the peripheral integrated circuit to be die bonded.
In the configuration of the solid-state imaging device 70 of FIG. 18, in addition to the step of applying the first adhesive 74 to the island-shaped layer 71, it is necessary to perform the step of applying the second adhesive 75 containing the filler 99 having relatively low viscosity to the first semiconductor chip 72. That is, it is necessary to perform two steps for separately applying different types of adhesives, thereby increasing the number of steps required.